No fines concrete is made by me using aggregate cement ratio 8:1 and water cement ratio is 0.43 Using light weight aggregate available from demolition waste, the density obtained is 290 kg/m3 Is it okay?
I need to use reinforcement in no fines concrete. How can I increase bond strength in no fines concrete?
I had answered this question long back. But the answer is not seen. Any way I reproduce the same as under:
The bond strength of no fines concrete is very low and therefore reinforcement is normally not used. Light weight aggregate possess high absorption capacity, Reinforcement can get corroded also.
If you still want to use the reinforcement for research purpose, the reinforcement should be completely coated with rich cement paste This will increase bond strength and also will not corrode.
If you get 290 kg/m3 of concrete density it is acceptable. Normally in no fines concrete with light weight aggregate you will get 375-400 kg/m3. You can go for aggregate cement ratio 6: 1 probably with this cement ratio you will be getting better results.
Dear Patel Ji,
No-Fines Concrete is a lightweight concrete made up of only coarse aggregate, cement and water by omitting fines (sand or fine aggregates) from normal concrete. The single sized aggregates make a good no-fines concrete, which in addition to having large voids and hence light in weight, also offers architecturally attractive look.
No-fines concrete is generally made with the aggregate/cement ratio from 6 : 1 to 10 :1. Aggregates used are normally of size passing through 20 mm and retained on 10 mm. The water/cement ratio for satisfactory consistency will vary between a narrow range of 0.38 and 0.52. Water/cement ratio must be chosen with care. If too low a water/cement ratio is adopted, the paste will be so dry that aggregates do not get properly smeared with paste which results in insufficient adhesion between the particles.
The bond strength of no-fines concrete is very low and, therefore, reinforcement is not used in conjunction with no-fines concrete. However, if reinforcement is required to be used in no-fines concrete, it is advisable to smear the reinforcement with cement paste to improve the bond and also to protect it from rusting.
I had answered this question long back. But the answer is not seen. Any way I reproduce the same as under:
The bond strength of no fines concrete is very low and therefore reinforcement is normally not used. Light weight aggregate possess high absorption capacity, Reinforcement can get corroded also.
If you still want to use the reinforcement for research purpose, the reinforcement should be completely coated with rich cement paste This will increase bond strength and also will not corrode.
If you get 290 kg/m3 of concrete density it is acceptable. Normally in no fines concrete with light weight aggregate you will get 375-400 kg/m3. You can go for aggregate cement ratio 6: 1 probably with this cement ratio you will be getting better results.
This article has some good stuff: http://www.ijifr.com/pdfsave/26-06-2015290V2-E10-055.pdf
No-Fines Concrete is a lightweight concrete made up of only coarse aggregate, cement and water by omitting fines (sand or fine aggregates) from normal concrete. Advantages, limitations and mix proportions of no-fines concrete is discussed.
Very often only single sized coarse aggregate, of size passing through 20 mm retained on 10mm is used. No-fines concrete is becoming popular because of some of the advantages it possesses over the conventional concrete.
The single sized aggregates make a good no-fines concrete, which in addition to having large voids and hence light in weight, also offers architecturally attractive look.
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Advantages of No-Fines Concrete
https://www.concretecentre.com/Performance-Sustainability-(1)/Special-Concrete/no-fines-concrete.aspx
https://www.irbnet.de/daten/iconda/CIB8837.pdf
I think that you should explain why you want to use reinforcement in no fines concrete.
Three ways I can think of would be the following;
1) Decrease the water cement ratio of the mix/paste.
2) Decrease the nominal aggregate size of the aggregate.
3) Use aggregate with more rough/angular shape.
I totaly agree with Dr K N Sheth and Kundan Meshram. In addition and in case reinforcement should be used and taking into account the possible corrosion of steel rebars; I'd recommend either using FRP rebars instead or using steel rebars coated with cement based bonding agent. In addition it is recommended to use rebars with relatively small diameters and large number rather than large diameters with small number in order to increase the bonding area.
When you don't use fine aggregate you may be produce pervious concrete and I think you mean bond between aggregates. To obtain stronger bond strength between aggregates you must be use clean coarse aggregates and more amount of cement and mineral admixtures such as fly ash and slag. Also, using of lower w/c ratio.
I feel the answer rendered by Prof Dr K N Sheth Sir is right and satisfactory.
these articles will help you:
Improving The Mechanical Properties of NoFines Concrete
SOME PROPERTIES OF FIBER REINFORCED NO FINE CONCRETE
An Experimental Study on Properties of No-Fines Concrete
Thanks to all Ola mam for your dynamic answer The article suggested by you are really useful.
it is advisable to smear the reinforcement with cement paste to improve the bond and also to protect it from rusting.
here you can find few articles could help you
http://www.ijifr.com/pdfsave/26-06-2015290V2-E10-055.pdf
http://qu.edu.iq/engjou/wp-content/uploads/2015/03/12-4-2012.pdf
Improving The Mechanical Properties of NoFines Concrete
In this study the mechanical characteristics of no- fines concrete with or without polypropylene fiber are investigated. The effect of mixture proportions on compressive strength , tensile strength and density presented. Result show that the addition of polypropylene fibers in no- fines concrete can improve the mechanical properties , especially the tensile strength, compressive strength by 19% and 17% respectively compared with the concrete without fibers, and a slight effect on the density. It was found that the strength of no- fines concrete is strongly related to its mixture proportion .A sealed compressive strength of 20.5mpa can readily be achieved with an aggregate /cement ratio of 3:1 / and 0.9 kg/m3 optimum quantity of polypropylene fibers. Adapted from ACI 213R-79, this type of lightweight concrete investigated from this research is considered structural lightweight concrete.
Thank you for your answer again Ola Adel I have seen the links Quite useful.
I also thank Nahla Hilal
Informative discussion. Dr. Dr K N Sheth gave Good explanation.
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